1. Field of the Invention
The present invention relates to an abnormality detector for detecting an abnormality of a motor drive system for use in a drive control, e.g., of a regulating valve of a circulation gas amount or an idle engine speed controlling intake valve, which are mounted in an exhaust gas circulation path of an automobile engine. More particularly, the invention relates to an improved abnormality detector for detecting an abnormality of a motor drive system by which it is easy to detect an abnormality such as disconnection, short circuit or the like in multiphase magnetic field coils themselves, driving open/close elements of the magnetic field coils, wiring between the magnetic field coils and the open/close elements or the like used in the motor drive system.
2. Description of the Related Art
As means for detecting an abnormality such as disconnection, short circuit or the like at a load itself, a driving open/close element, wiring between the load and the open/close elements or the like with magnetic field coils for a stepping motor being the load, a variety of attempts have been disclosed. A typical method thereof is as follows:
A. Load Current Detection Method
This is a method for monitoring a voltage drop generated at current detecting series resistors at the time of power-conducting magnetic field coils acting as a load, and determining whether or not an appropriate current flows. This method is for detecting an abnormality at each part from an overall standpoint by utilizing a fact that a load short circuit, a wiring short circuit or the like causes an excessive current flow, while a load disconnection, a wiring disconnection, a closed circuit abnormality or the like allows only a current of less than a predetermined value to flow.
This load current detection method is effective also in order to prevent the open/close elements from being damaged as a result of automatically interrupting the open/close elements when a short circuit abnormality occurs at the load or wiring. In the case, however, where an electrical load is an inductive load, a delay in current elevation usually takes place just after power-conducting the open/close elements and, therefore a delay detection processing is required so as not to determine impatiently such a state of current elevation as a disconnection abnormality.
B. Leakage Current Detection Method
This is a method for connecting resistors of a high resistance through which a leakage current flows, in parallel to load driving open/close elements, and monitoring a dividing voltage at the resistors of high resistance. Supposing that there is no leakage current flowing to the load when interrupting the open/close elements, an abnormality at each part is detected in an overall manner as a disconnection in load or wiring, or a short circuit abnormality in the open/close elements.
C. Surge Voltage Detection Method
This is a method for detecting a surge voltage generated by an inductive load, at the time of interrupting the load driving open/close elements. Supposing that there is no surge voltage, an abnormality at each part is detected in an overall manner as a disconnection in load or wiring, an interruption abnormality at the open/close elements and an interruption abnormality due to the short circuit in load or wiring. Also in this surge voltage detection method, a delay in generation of surge voltage takes place just after interrupting the open/close elements, and therefore a delay detection processing is required so as not to determine impatiently such a state as a abnormality.
The Japanese Patent Publication (unexamined) No. 203599/1991 (JP No. 2639144) titled xe2x80x9cExhaust Gas Circulation Valve Controllerxe2x80x9d (literature) discloses an example of a drive control for a stepping motor based on the the mentioned load current detection method. The Japanese Patent Publication (unexamined) No. 257799/1998 titled xe2x80x9cOutput Open Detector for Multi-Channel Output Devicexe2x80x9d (literature B) discloses an example of a drive control for a stepping motor based on the mentioned leakage current detection method. The Japanese Patent Publication (unexamined) No. 99796/1995 titled xe2x80x9cDrive for Stepping Motorxe2x80x9d (literature AB) discloses an example of a drive control for a stepping motor employing both of the mentioned load current detection method and leakage current detection method.
On the other hand, publicly known abnormality detection means for a plurality of electrical loads are broadly classified into: an external hardware method, in which a result obtained by carrying out determination and synthesis with the use of a hardware (H/W) is fetched in a microprocessor; and an internal software (S/W) method in which a synthesized state signal is inputted to the microprocessor, and a determination processing is carried out inside of the microprocessor.
In the mentioned literature A, an external H/W method is disclosed, in which an abnormality as to four magnetic field coils of a stepping motor is delay-latched, and after AND-connection thereof, a result of synthesis abnormality determination is fetched in the microprocessor. In the mentioned literature B, an external H/W method is disclosed, in which a normal state signal as to four magnetic field coils in a stepping motor are OR-connected by means of a diode, an integral circuit is reset using an output signal from the diode, and an output from the integral circuit can be fetched in the microprocessor as a result of synthesis abnormality determination when required. In the mentioned literatures AB, an internal S/W method is disclosed, in which various state signals are logically connected and inputted to a microprocessor, and a period and a duty ratio of the inputted pulse train are monitored in the microprocessor, whereby detection of disconnection and short circuit is carried out.
As a further known art relating to this invention, the Japanese Patent Publication (examined) No. 92016/1995 titled xe2x80x9cFailure Detection Circuit of Fuel Injection Valve Drive Circuit for Internal Combustion Enginexe2x80x9d (literature C) discloses an example of a drive control of an electromagnetic coil for fuel injection valve drive based on the mentioned surge voltage detection method.
Furthermore, in the Japanese Patent Publication (unexamined) No. 18315/1993 titled xe2x80x9cAutomobile Engine Control Apparatusxe2x80x9d (literature D), it is described that, in order to carry out initialization of an actuator which is drive-controlled by a microprocessor incorporated in an engine control apparatus, a power is fed to the engine control apparatus via a power supply relay driven by a power supply switch, operation of the mentioned power supply relay continues even after turning OFF the power supply switch, and the power supply relay is interrupted by ending the initialization.
Among the various conventional arts as described above, the external H/W method shown in the literature A or B has a disadvantage from the view points of dimensions and cost, whereas the internal S/W method as shown in the literature AB may be desired in such viewpoints. However, in the art disclosed by the literature AB, there is no concept of specifying which load system falls within an abnormality among a large number of electrical loads, eventually resulting in a disadvantage of making it difficult to carry out a maintenance work.
Moreover, it is certain that any abnormality in the magnetic field coils, the open/close elements, the wiring or the like can be detected in an overall manner when applying the surge voltage detection method disclosed in the literature C to multiphase magnetic field coils. A problem, however, exists in that when synthesizing surge voltages in multiphase magnetic field coils in parallel, it becomes difficult to extract and detect an abnormal phase as long as the stepping motor is driven at a high speed.
A first object of the present invention is to provide an abnormality detector for motor drive system capable of making a maintenance work easy by using an individual state detection signal provided by an external H/W simply at a reasonable cost through a detection of a surge voltage, and in which the individual state detection signals are logically combined to constitute a single synthetic state detection signal and inputted to a microprocessor, an appropriate abnormality detection is carried out by a S/W processing in the microprocessor while avoiding abnormality detection during operation at a high speed, and an abnormal load system can be specified.
To accomplish the foregoing first object, an abnormality detector according to the invention includes: a plurality of open/close elements that, in response to an interrupt signal generated by a microprocessor, energizes multiphase magnetic field coils in a predetermined order and drives a stepping motor in forward/reverse rotation; individual state detection means for each phase; synthetic state detection means for all phases; temporary storage means; individual determination storage means; reset means; and abnormality alarm display means. The mentioned individual state detection means detects individually a surge voltage for each phase, the surge voltage being generated at the time of interrupting the power conduction through the mentioned magnetic field coils by the mentioned open/close elements, and confirms power conduction through the mentioned magnetic field coils or interruption thereof. The mentioned synthetic state detection means logically adds signals detected by the mentioned individual state detection means, and generates a synthesized signal in order to confirm power conduction through the mentioned magnetic field coils or interruption thereof for all phases. The mentioned temporary storage means stores generation of a synthesized signal detected by the mentioned synthetic state detection means. The mentioned individual determination storage means reads out a content of the mentioned temporary storage stored with an interval of a fluctuation delay time immediately after an initial rise or fall of the mentioned interrupt signal following a pause for not less than a predetermined time of the mentioned interrupt signal at the moment of a next rise or fall of the mentioned interrupt signal, and stores presence or absence of an abnormality (whether or not there is any abnormality) for each phase. The mentioned reset means deletes the content in the mentioned temporary storage means after the mentioned individual determination storage means stores presence or absence of an abnormality for each phase at this time, and enables a synthesized signal generated at the next time to be stored. The mentioned abnormality alarm display means operates an abnormality alarm display in response to a fact that at least one of the mentioned individual determination storage means stores any abnormality. Further, the mentioned individual determination storage means stores, for each phase of which power-conduction has been interrupted, a fact that any synthesized detection signal of the mentioned surge voltage is not generated upon initially interrupting the power conduction after the mentioned stepping motor pauses for not less than a predetermined time, and carries out an abnormality determination at the time of starting a forward/reverse drive of the mentioned stepping motor.
As a result, number of signals to be processed is reduced thereby making a hardware constitution inexpensive and simple. Furthermore, even if the detected surge voltage comes to form a seamless and continuous waveform at a high-speed operation of the stepping motor, abnormality for each phase can be detected without fail.
A second object of the invention is to provide an abnormality detector for motor drive system capable of making a maintenance work easier, and in which using an individual state detection signal provided by an inexpensive and simple external H/W for detecting a surge voltage, a plurality of synthetic state detection signals obtained by connecting logically the individual state detection signals are inputted to a microprocessor, thereby enabling an abnormality determination during a high-speed operation, and exact abnormality detection is carried out by a S/W processing in the microprocessor, and an abnormal load system can be specified.
To accomplish the foregoing object, an abnormality detector for motor drive system includes: a plurality of open/close elements that, in response to an interrupt signal generated by a microprocessor, energizes multiphase magnetic field coils in a predetermined order and drives a stepping motor in forward/reverse rotation; individual state detection means for each phase; first and second synthetic state detection means for detecting first and second synthetic states; temporary storage means; individual determination storage means; reset means; and abnormality alarm display means. The mentioned individual state detection means detects individually a surge voltage for each phase, the surge voltage being generated when interrupting the power conduction through the mentioned magnetic field coils by the mentioned open/close elements, and generates a detection signal in order to confirm power conduction through the mentioned magnetic field coils or interruption thereof. The mentioned first and second synthetic state detection means logically adds signals in a group, which does not operate adjacently, among the signals detected by the mentioned individual state detection means, and generates a synthesized signal in order to confirm power conduction through magnetic field coils or interruption thereof for each group. The mentioned temporary storage means separates the synthesized signals, which have been detected by the mentioned first and second synthetic state detection means, at least for each group, via a first and second interrupt input terminals, and stores the separated signal in the RAM memory in the mentioned microprocessor. The mentioned individual determination storage means reads out a content of the mentioned temporary storage stored for each group with an interval of a fluctuation delay time immediately after a previous rise or fall of the mentioned interrupt signal output for each group at the moment of a rise or fall of the mentioned interrupt signal this time, and stores presence or absence of an abnormality (whether or not there is any abnormality) for each phase. The mentioned reset means deletes the content in the mentioned temporary storage means after the mentioned individual determination storage means stores presence or absence of an abnormality for each phase at this time, and enables a synthesized signal generated at the next time to be stored. The mentioned abnormality alarm display means operates an abnormality alarm display in response to a fact that at least one of the mentioned individual determination storage means stores any abnormality, and enables the abnormality determination in a state of the mentioned stepping motor being continuously driven at a high speed.
As a result, a surge voltage acting as a detecting signal for each group shows an intermittent waveform even when the stepping motor operates at a high speed, thereby enabling the abnormality detection for each phase. Furthermore, number of signals to be processed is reduced thereby enabling simple and inexpensive abnormality detection.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.